Enhanced Joule Thief with LDR

Add an LDR to your joule thief and enjoy a whole world of additional usefulness. From day/night functionality all the way up to a joule thief megaprocessor.

[@JerryEricsson]

I have been playing with Jule Thieves for some time, all of them are back in South Dakota right now and i am in Arizona so I don't have access to them as I type, however I was amazed to find that I could light a 1 watt LED with one I built it using a ferrite choke that I removed from an old laptop power cord, you know the kind they are about an inch long an large enough to put a power cord through. It was very easy to wind, and looks great with the rest of the thief sort of strapped around the core. I put a small slide switch on her and mounted the whole shebang on a AA single cell holder. I replaced the 1 watt with a regular blue LED after experimenting with it, now the 1 watt is glued to a 2 cell AAA holder with built in switch. I have no idea how long the batteries are going to last, I have had it now for over 6 months laying beside my work table, and use it when ever I need extra light to read transistor or IC numbers, it is very bright for 2 AAA's in fact the other night i used it to light up the entire living area of our motor home when the power went out. It was on for over a half hour and the cells still seem to be in great shape. No heat issues either. LED'S are indeed fun to mess with. Thanks for developing my interest in the field!

[@RWBHere]

I've been making Jouke thief circuits for some years now, using quite tiny ferrite beads such as those which fit over a wire as a filter. The number of turns is about 5 or 6, which is as many as could be threaded through the centre of the bead. They work well. Your enhancement is a good idea,mand it will be added to those unswitched 'children's night lights'! Thanks Julian.

[@paradiselost9946]

i used one with an isolated winding with 4x turns to get a 22v supply for lil miniature russian tubes. try as i did, i couldnt get any higher under load. power the filament straight from the nimh, yet still run cathode follower with bootstrapping. very tricky to do when its a directly heated cathode. even harder when its a pentode. makes a great pre-amp for an acoustic guitar. need the bootstrap to impedance match the piezo pickups.

[@andybaker2443]

I loved your thoughts on logic gates; and as always your whole video.

[@ThatGuy-nv2wo]

As soon as you mentioned the inversion, I knew you were going to get some crazy idea to make a joule thief computer... Not practical at all, I love it!

[@JulianIlett]

Don't forget the joule thief ring oscillator :)

[@ThatGuy-nv2wo]

Oh gosh, I can't wait!

[@maicod]

Julian Ilett busy times :)

[@joeyocom5087]

It took a bit, but I wound up using a 10k pot. Works like a charm. Thank you !!!! I have been trying to find out how to do this since I found out how to build a Joule Thief

[@joeyocom5087]

I figured out how to run certain 2 pin RGB LEDs on a Joule Thief. I am getting a stable DC reading !!!!!! one 104 ceramic cap & 2 switching diodes.!!!!!!!!!!!! Thanks to you I can make it solar after getting some 12 mm LDRs, 2 in parallel for better low light. Stays off longer !

[@maicod]

I've got a couple of torches only very slightly bigger than one 1.5 V AA or AAA cell and the LED works. I've always wondered where they hide the ferrite ring. I guess it uses a tiny boost chip instead ?

[@hrnekbezucha]

We must imagine Clive happy

[@jimsmind3894]

Love the joule theif. Such a simple yet hard to understand circuit. If you cover it again, would be cool to see if you could improve the efficiency of the basic design. I think there's a few circuits around with a cap in there too.

[@cliftonbrown911]

Julian, Excellent as usual. Wondering if a part of the joule thief circuit in combination with a super cap could increase the efficiency of a solar charging circuit in a very low power LoRa sensor with a small solar panel?

[@mduvigneaud]

Awesome, Julian! And I love that tiny breadboard. It's the cutest thing! :D The smallest ones I have are the 17 rows with 2 columns of 5 (I don't know the correct terminology.)

[@juncusbufonius]

How did the current go down on what appears to be the same circuit as the previous video? There it was about 17ma and only went down to 16ma when the led was out of circuit. What changed the efficiency and was the ldr responsible for the off circuit reduction?

[@JulianIlett]

I remember that. The LDR will kill any oscillation in the circuit - removing the LED probably doesn't.

[@PunakiviAddikti]

I've discovered that rectangular, premade transformers with a rectangular ferrite loop also work wonders. Salvaged some from an old VCR.

[@_Piers_]

What would happen if the LDR could "see" the joule thief's LED? I assume it would switch on and off, but I wonder how fast. Would it be switching fast enough to act like PWM, reducing the effective brightness?

[@charliedobbie8916]

The LED is already switching on and off rapidly in a Joule Thief! Interesting question about self-activation though, worth trying.

[@raykent3211]

Pook365 ldr's are sluggish, around 20ms or longer response time, which would give an oscillation below 50 hertz.. Could be an interesting design for a low frequency oscillator! I'd guess that the output would be approximately sinusoidal, which ain't that easy at low frequency. Then again, it might just fail. I shall ask my lawyers to serve a legal demand on Julian to do this and put his scope on it.

[@johnf3326]

Could do with a joule thief in my Roberts DAB radio, takes 6 D cells and gets distorted when the voltage drops

[@rich1051414]

Could you use the photoresistor and the LED pointing at it as the oscillator?

[@DAVIDGREGORYKERR]

what about using two BC182L transistors as a ROYER oscillator and use that to somehow power the LED.

[@capri2wd]

nice upgrade to the trusty old joule thief.

[@majdinj]

Hi Julian; Have you tried HH004F in to-92 package for Joule thief circuit? The circuit will only need any inductor (the one like resistor will do) and you are good to go.

[@FurrBeard]

Thank you for that! I've always wanted to play with a Joule Thief or the like, but *hated* having to wind wire around those dratted ferrite cores; the HH004F makes things so much simpler using an ordinary inductor.

[@generalawareness101]

Am I right that the larger the LDR the more sensitive it is, and that is the only reason of the larger sizes? If I remember the 1980's when I played with some they had varying resistances but when I look around now all the Chinese ones are the same.

[@HobkinBoi]

Question, would this work for a flashing joule thief? I've made mine flash and I would like it to blink in the dark. The circuit is nearly exactly the same as yours, but instead of a 10k resistor, it's a 60k with a 22uf capacitor in parallel with the resistor.

[@barefoot69]

How many milliamps does the circuit use when the LED is off ? I guess about 1mA. Not ideal if you're trying to extend the battery life.

[@MrBuck295]

for the inductor /transformer what would be the minimum amount of turns for it to work alternately what would be the maximum for efficiency or for it to stop working I know the size of ferrite ring and wire gauge would be the variables but for one given size (using the same ring with the same gauge of wire ) has anyone ever tried to determine these

[@MitkoNikov]

I suppose, there are a lot of things that can work as gates, but this one is kind of......... What is the light level difference of the LED though, with and without the LDR?

[@birnodin]

If the LED would shine on the photoresistor the LED would go off. Then the photoresistor changes his resistance and the LED would go on. Then .... Please try it, will it be the "Joule Oscillator" ?

[@kevinkenyon2490]

What is the highest amount of voltage you can put into a jule theif?

[@joshwayop5413]

julian ilett, if you put a varible resister between the resistor and the base of the transistor u can change the brightness of the led

[@JerryEricsson]

Howdy once more, question from the peanut gallery - I love tearing down exotic boards, so when the Carbon Monoxide Detector timed out (they shut down after 5 years usage according to the book!) I replaced it, and now have the perfectly good but self shut down board. I intend to salvage what I can from it before disposing of it. One of the interesting chips was a Motorola micro-controller MC68HSR705J1A I downloaded the data sheet and she looks like she could be used again for some fun project. Do you have any idea who I could program the little chip to, perhaps turn on and off an LED or some such fun project which could lead to, perhaps powering a small LCD or some such joyful endeavor? Since I am, at this time, setting in the middle of the Mohave Desert in Arizona, 1500 miles South West of my sticks and bricks home in South Dakota, I find myself with no resistors (forgot my supplies cabinet!) so when want to make a simple project with an LED I am SOL. So I looked at this board and man she has dozens of the little critters, all through hole but they may be difficult to harvest as she is double sided but that makes life more interesting I guess. the Motorola chip is socketed so she is an easy pull.

[@GrandadIsAnOldMan]

Brilliant video Julian and well explained 😊

[@raykent3211]

GrandadIsAnOldMan I subscribed to your channel and haven't had a notification for more than a year. Very pleased to find you're still going!

[@davidb1669]

If you don't want to wind an inductor yourself, you can use two through hole inductors as your center tap. You can play around with the values, but the biggest variable I've seen is the position of the two inductors relative to each other. If you move them around each other, you can very easily see the result in the LED brightness.

[@vylbird8014]

A daylight switch needs hysteresis to prevent oscillation. I know a pretty good circuit for it, uses just one op-amp and a few resistors to form what is essentially a one-bit memory cell, plus a power transistor to drive the load.

[@maicod]

you created an opto-coupler ;)

[@tonysansom]

Maico Although, wouldn't it actually be an inverted opto-coupler...or...Nopto-coupler?

[@isoguy.]

Just incredible lateral thinking. Any ideas fot a desktop fusion reactor?

[@joeyocom5087]

solar recharged......I have it working in my window

[@barrygreengrass3379]

Julian can you use any LDR or do you need a specific value LDR?

[@johnmorgan1629]

Linus Tech Tips, did a video on the Apollo computer, including close up shots of the computer cores of the guidance system, which showed the ferrite wound matrix. There was another KZbinr with him (cannot recall who), they even got to talk extensively to one of the original engineers who worked on the system.

[@drank4069]

3 way joule thief ring oscillator anyone?

[@RWBHere]

Yes please! It would be interesting to see at what speed it could run.

[@BillAnt]

I believe if you connect a cap in parallel with the resistor on the base of the transistor, you should be able to control the frequency/duty cycle of the oscillator to some degree (R/C). I've seen someone else experimenting with that. Blocking oscillators seem to be an overkill as far as being used as a logic gate, which can be accomplished much simpler by a single transistor and a bias resistor (pull up or down).

[@km5405]

julien, ever heard of the two-transistor circuit? it uses a regular inductor some resistors a capacitor and a NPN and PNP transistor (I hear its similar to the DC-Dc circuits uses in solar garden lights) ... mine works like a charm :D.

[@_who_cares_1123]

A joule thieve computer would be awesome to look at! Imagine all the flashing LEDs

[@thewhitefalcon8539]

You don't need a joule thief, just use a power supply that has enough voltage, and then you've reinvented RTL.

[@TheMechanator]

Is it possible to take the voltage output to the LED and use it to recharge another rechargeable battery? Given that the forward voltage is about 2.1-3.5V for the led at about .017-.030 A. ? So you could suck those alkaline cells dry and get a freshly charged Nimh or Nicad battery out of the pile of "dead" batteries. I bet this recharged battery of 1.5V could then be plugged into another houle thief to electroplate small items with a brush and working electrolyte solution. Also the Joule thief to charge a small battery could be ran from a small solar cell(s) even in dim light from indoors or cloudy days? Neat!

[@Yoshi247]

Try make a few more and place them in a loop.

[@JulianIlett]

You read my mind :)

[@maicod]

omg you're a real electronics-naughtyness invoking person Julian

[@JanJeronimus]

Solar powered using super capacitors?

[@JulianIlett]

You also read my mind - charge during the day - compute at night - already ordered a load of 10F capacitors :)

[@gordonlawrence4749]

I could be wrong but I am under the impression that there is a bit of a compromise on the transformer. IE you want as small a ferrite as possible, as many windings as possible and as thick wire as possible.

[@joeyocom5087]

I got a fast RGB to work in a joule thief circuit but the AA cell has to be almost dead for it to run a fast RGB in it's usual pattern, but the pattern and light suffered. There is not much light & slowly goes through the pattern, so it does not run correctly. The slow changing LED seems to work better at higher 1.2 current, but not like the $1.00 garden RGB solar stake light circuit. I am Running a 104 ceramic cap & switching diode.... just like the dollar store circuit . I Need Help !!!!!! You can use lower inductors , 1 lumen? ( 1 $ dollar store inductors) In these and use Slow Or Fast RGB 5mm/ 10 mm LED and make them last all night on a 700 mAh cell. With the dollar store inductor you get more light out of the RGB 40 mAh stake lights but you do not get the power drain from the Lowe's light's inductors...ugh !!!! If these are still built the same they will Run color changing & flashing LEDs I have slow changers on my Back deck lights www.lowes.com/pd/Portfolio-2X-2-Light-Black-Solar-LED-Railing-Light-Kit/999928382

[@travismoore7849]

What if you replace the transistor with a blinking led that uses avalanche breakdown to blink?

[@309electronics5]

The chip inside wont get enough power cause its still powered from under 1.2 volts

[@paranoiia8]

I love photo-resistors and movement detectors, they are really cheap and really easy to implement in almost everything. You can even buy cheapest night light that you plug to the wall or those battery light for wardrobe that light up when you open it, and without too much work you can just gut-out it and put anywhere, most of work on 4-12v and they are really efficient. I have one in bathroom converted to 9v battery with small resistor and it work for almost half year and still is bright as new. Those photo-resistors and motion detectors are really nice to slightly reduce power consumption in home. Because you dont really need to turn on light at night if you go to bathroom or other room, you dont need to turn on light when you get up from bed looking for slippers, because you can put light on wall or under the bed, you dont need to turn on light in the kitchen just to get spoon. So many ways to use it... In last Christmas I spend few days converting all those cheap led strings lights to have light sensor and when normally battery die after 2 days if you forgot about turning it off, with those light running on 3 AAA, can last even week. Its so cheap I have no idea why people dont use it more often, especially that they use LED bulbs anyway.

[@joinedupjon]

8:55 really needed the first bar of the 2001 theme in here... you could make it a regular thing when you come up with an improbable nand/nor gate circuit :)

[@bertoid]

I was very surprised, given your previous video, that you didn't face the LDR to the LED and look for oscillations?! I'm thinking that if you try a high value resistor (say 10K-100K) from base to emitter, it may help minimize the dark state current, since the coil-resistor-LDR is always turning the transistor on a little.

[@pileggitech]

The end of this video was hilarious!

[@sham1234567891]

Nice circuit. Could you please specify the number of turns for each coil on the ferrite ring? I can't find reference to same. Thanks.

[@charliedobbie8916]

Traditionally, twenty turns. Note that it's twenty *double* turns though!

[@sham1234567891]

Thanks. Got some QX5252F that work differently at dusk or dawn. When sunlight gets dim through the solar cells, the QX5252F senses the voltage drop and triggers the battery circuit. Anyway, both are very useful and have their own niche. Great forum.

[@JasonMasters]

I've used from 35 to 45 turns, but as stated, less turns will also work. This circuit is very non-critical in that respect.

[@karimismail3734]

Other Videos show minimum 4 turns or more.

[@acsonpc]

What's the value of inductor ?

[@rflberg]

Sticking the LDR across the emitter base junction would not really turn off the circuit because it would complete the circuit on the base resistor causing a small current drain that does nothing.

[@russellhltn1396]

Hence the 100 microamp draw when off. It's not perfect, but how would you do it given that the resistance goes low when it sees light?

[@karimismail3734]

This is a simple circuit to test. Don't expect miracles my friend!!!!

[@spikeydapikey1483]

Now that is a handy little mod!

[@RWBHere]

2000jago, watch the video.

[@pileggitech]

I see you everywhere...

[@joeyocom5087]

If you run the resistor through the photo resistor in series to the Transistor collector, it will go out in the dark

[@paradiselost9946]

a toroid will give a longer pulse, same energy but at a lower overall potential as the magnetic field doesnt collapse so fast. the straight ferrites, usually in SMPS supplies wrapped in a bit of heatshrink... they make really snappy pulses with high peaks, better for driving several LEDs in series. theres also a spike back on teh base, can throw a LED there. i tend to use my LED like a freewheel diode, across the coil. this way it also works on higher voltages. LEDs dont mind being overdriven with pulses, they limit the current/voltage themselves when theres a restricted supply of power, such as in a pulse. they smoke when the power is continuous... or at least, over the duty cycle. so you cant run a higher voltage with the LED where it traditionally is.

[@JasonMasters]

Julian, you neglected to mention that most of those CFL circuits also have a cylindrical choke which can also be re-wound to make a Joule Thief transformer. In fact, there is so much wire on the choke that you can re-wind the choke with some of the wire and use the rest to wind onto the toroid, and still have wire left over. Two Joule Thief transformers from a single broken CFL. :) You know those cheap LED strings which use two AA cells in series? I've modified three of those to run off a single AA cell with a Joule Thief circuit tucked into the space where the other AA cell would have gone. In the ones I bought, I found it easy to pull out the battery terminals and solder a wire to the bridging terminal which previously joined the two cells in series. Subjectively, it appears as though a single AA cell lasts about as long in a Joule Thief circuit as two AA cells do alone, so I'm getting something like double the battery life. I usually use 35-40 double-wound turns to give 70-80 turns with a centre tap. When winding the cylindrical choke, I usually find it easier to wind the 35 turns, then make the centre tap, then wind another 35 turns. When winding the toroid, I usually find it easier to fold the wire double and wind the 35 turns that way, so I do both windings at the same time. The only "trick" to watch for when double-winding is that you can't use the folded end as the centre tap since the windings would be going contrary to each other thus cancelling out the magnetic flux.

[@NNNILabs]

Hmmm.... I thought you replaced the base resistor with the LDR so that the base current of the transistor varies with the LED brightness in some kind of a regulated circuit when I first read the title.

[@joeyocom5087]

I put 2, 12 mm LDR in parallel and it stays off longer in low light

[@joeyocom5087]

As far as the torroid coil wire: the insulation needs to be as thin as possible and wound tight to the ferrite ring

[@koz]

This is really interesting. I wonder if it has enough power for an ESP8266 (or even ESP32) microcontroller? Very much enjoying your videos. It's re-ignited a passion for all this stuff since I was a lot younger. And now my dining table resembles an electronics workshop. So thanks for that too! :) Also, regarding the ferrite rings: I've seem people use a 3d printer with iron infused filament to try and make their own cores. Neat idea!

[@JulianIlett]

Oh cool :)

[@aldebaranflash2663]

Good Job.

[@realflow100]

this is like almost half of a DC to AC 12v to 110v converter! just need a winding on the output of the transformer. to convert it into higher voltage AC

[@R4MP4G3RXD]

You never got around to doing the opto-isolator computer, so not really expecting a joule thief computer. Would be interesting tough.

[@mikerhodes9198]

How long with a 1.5 volt battery light the LED? Hours? Days?

[@charliedobbie8916]

Usually days to weeks, depending on how much charge was left and how well the circuit is operating.

[@krisztianszirtes5414]

A practical use for this could be a circuit that works from a single cell and works with a PIC or ARM that needs 3.3 on the logic signals and on the power pin

[@mynameisnobody1fjb372]

OK, you mean as a power supply, I think, the Joule thief operates from nearly exhausted cells, you would not be able to run the micro controller for long, maybe you have a different thing in mind.

[@mr.amp0076]

Jule's thef computer...... Hahaha... 😂😂😂

[@Narsandorin]

Can jou make a solar lamp from it

[@Durrdalus]

The small ferrite cores are quite cheap on fleabay so no need to go to your local recyclers to grab some dead cfl bulbs!

[@TheBlackadder-Edmund]

Salvaging components from fluorescent lamps (I have done this, I love to salvage components): BE CAREFUL, do not break the glass parts, very nasty stuff inside that you could breathe in. No, I have not broken any. Thanks for the video!

[@Mark1024MAK]

TheBlackadder Edmund The amount of nasty stuff inside modern CFL is very small, and even less so from a worn out lamp. So although it recommended not to break the glass, it's not a big deal if the glass does break. If the glass does break, open a window to ventilate the room, put gloves on, and carefully dispose of the broken glass.

[@DonaldSleightholme]

I’ve had a idea that you could use a transistor to turn a electro magnet on and off to move the strong magnet in and out of a coil of wire 🤔 (when it’s on the magnet would be attracted to the electromagnet and when it’s off gravity would pull it back down) if the circuit was powered by sunlight you would get more electricity this way and DC to AC conversion 😮

[@RWBHere]

No, you would use much more electricity than could ever be generated by trying to use a small amount of electricity to move a mechanical device. Save the power from solar cells in a modern battery or a large capacitor instead, and lose much less of it.

[@arifanwari3168]

Donald Sleightholme gravity does not exist buddy

[@WilliamDeboer]

Should be able to use one of those color changing leds right?

[@charliedobbie8916]

No: the Joule Thief is switching the LED on and off rapidly, so a color-changing LED would continually be restarting. It would just appear red (or whatever the initial color is)

[@WilliamDeboer]

Charlie Dobbie ahh ok thanks for the explanation

[@stb68]

I believe you can add a capacitor to smooth the output to get around that issue, which is presumably what the colour changing solar lights do.

[@WilliamDeboer]

S Butler worth a shot I suppose.

[@i.apilado]

Why don't you put 100pf capacitor parallel to the resistor, the current or voltage will increase.

[@sangwinc]

The joule thief computer is no more bonkers than the OU's "Bobcat" ball bearing computer.......

[@tyttuut]

You should call it a _Julian_ thief! *laugh track*

[@charliedobbie8916]

That's a looooot of winding of inductors! Fiddly enough when I made one, wouldn't like to be making fifteen thousand of them...

[@benwinkel]

It's the logical thing to do. Live long and prosper!

[@JohnJohn-gy2st]

Hello How to make led

[@himselfe]

Now just combine a crystal radio circuit with a joule thief circuit and make the world's first self-powered computer!

[@hinzster]

Next: Julian orders several thousand LEDs from ebay.

[@niniliumify]

Making some throwies?

[@dennisseuferling815]

OPTO-ISOLATED NOT GATE!!! That's brilliant.

[@AnotherBrokenToaster]

Make a ring oscillator with them :D

[@Real_Tim_S]

I wouldn't recommend this method for day-night switching on the joule thief if you don't want to replace batteries often - the LDR as you have it in your schematic now shunts the base to ground, meaning that the current will still flow from the battery through the coil and the resistor completing the circuit to ground through the LDR (DC load, not AC like the normal operation of the circuit). This means you'd be drawing 0.15mA constantly even while the LED is off. IMHO, it would be better to find a way to switch off the power to the Joule Thief with something else - maybe a low-power/low-drive-current comparator (thanks to smartphones, they are available with stable operation below 0.8V) and a photodiode or a small solar cell to trigger without drawing power.

[@johnmoor8839]

what about the resistance of the LDR itself plus any the coil may have?

[@calo1059]

Make a hartley ocillator and conect led across coil

[@raykent3211]

Some here may like to puzzle... I watched a video the other day about the difficulty of getting A I to learn the xor condition from data. Puzzle: how should a 3 input xor gate behave? The answer/s is/are in wiki.

[@derknistermann5613]

Look.at.that.tiny.bradboard.:33333

[@thehappylittlefoxakabenji8154]

could be a bread crumb or a crouton !

[@morlanius]

Should have used a photodiode instead.

[@yoeribolderdijk1257]

Or you use a common mode choke, the lazy way :D

[@xanataph]

Are there any more awkward ways to create logic circuits while still remaining in the domain of solid state? How about this: Carbon microphones from old telephone handsets taped to small speakers. Add a few resistors and you could run the sucker from low voltage AC! lol

[@raykent3211]

xanataph you shouldn't put an idea like that on KZbin before getting a patent.

[@xanataph]

I get your point, but I really couldn't be bothered developing the idea myself, but it would be interesting to see someone else try it out! lol I have other ideas for carbon mics, that I will keep to myself and maybe one day even use 'em..! :)

[@gcewing]

Frog's legs operating microswitches.

[@raykent3211]

Greg Ewing yeah, sadly frogs' legs are wet, so it's not quite solid state. Nice idea though.

[@pleasecho2]

5252F: the end of the joule thief?

[@SidneyCritic]

More serpentine than Zag-Zig. lol

[@mrtom64]

NOR gate = BOTH inputs are negative? Surely the term 'OR' implies either, not both....doesn't it? Isn't that definition for an XNOR gate?

[@Graham_Langley]

NOR = OR followed by inverter - hence the symbol.

[@ThatGuy-nv2wo]

NOR gate is such that if any input is high, output is low. It's an OR gate with an inverted output, hence NOR

[@russellhltn1396]

At risk of pile-on, my understanding is that it's "Not OR". "Not" being a term for "the opposite" or "inverting". Likewise a NAND is a "Not AND", that is an AND gate with an inverted output.

[@twotone3070]

NOR = A or B or BOTH but the output is inverted, so any '1' on an input gives a '0' output. XNOR = A or B 'exclusively' and the output is inverted. I felt the first paragraph of that wikipedia entry confused the issue in referring to negative inputs, rather than negating the output, which is where we indicate the 'N' part of the NOR on a diagram symbol. Perhaps just the way I have chosen to easily remember it?

[@ArixZajicek]

Not A NOR B can be active. Think of it like that.

[@krisztianszirtes5414]

Enhanced Joule Thief with Long Distance Relationship

[@bertoid]

For the JTComputer, you'll need small size and ease of construction. I just stumbled on this which uses 2 very small smd inductors (and so no toroid), and even no resistor (but it'll still need the LDR): kzbin.info/www/bejne/nWPNfqWEe7tnpLM I imagine that each element, being more "active", will have a better fanout than the optoisolators did.

[@tubeDude48]

It would be best if authors would give wire gauge and number of turns. I don't understand why that is ignored so much!!!

[@AlexanderWright1]

It's ignored, because it doesn't matter that much. It's only pulling 20 mA max, so thin gauge or thick is fine. Each pump of the oscillator only shifts a very small amount of charge, so you don't need many windings around the core.

[@rizkyp]

Build ALU with joule thief.

[@AndrewGillard]

This mod completely negates one of the main features of the Joule Thief: that once it's started running from a cell around 1.3V (I don't exactly recall the minimum starting voltage), it'll stay running down to around 0.4V. By turning the transistor off with an LDR, it will only light again with a relatively-high voltage cell (1.3V or whatever it is), not an almost-dead one, which was the main benefit of the circuit.

[@JulianIlett]

Working fine at 0.9v :)

[@JulianIlett]

Working fine at 0.8v :)

[@AndrewGillard]

Interesting! I wonder what makes that work, then. Clive's video said that you need a fairly high trigger voltage to light the LED initially but that it'll run down very low after that, so your modification seems to run counter to that. I'm happy to be wrong in this case :)

[@JulianIlett]

Still working entirely reliably at 0.65v :)

[@user-jp1yd2ut9r]

why not put a joule thief into another joule thief and keep stacking them lol

[@galen__]

Photonic Computer 😅

[@DupczacyBawol]

People! Never connect LED to power supply without a resistor in series! Sir Julian is teaching you bad things, again!

[@karimismail3734]

Not necessary here. As soon as there is enough voltage to turn on LED it will light up. No extra energy goes thru to burn LED.

[@karimismail3734]

I also made same connections on BreadBoards with no Resistors. Never burned an LED. Do you also know that you can connect 3 or 4 LED's. It works.

[@williamsquires3070]

Answer: no. The problem is they’re oscillating. Once you try cascading elements, you’re going to run into a nasty problem.

[@Fourcycle]

Which can be fixed by adding a diode and capacitor to filter the current to the LED. Color changing yard lights use this since the color changing LED's reset when powered down and back up. It sure drives up the parts count though!

[@DonaldSleightholme]

could build a processor that uses light and it would be much quicker maybe? 😮

[@DonaldSleightholme]

using fibre optic instead of copper 🤗

[@DonaldSleightholme]

i suppose that processors already use optics if they are made from silicon wafers 😔